How to Make a Telegraph Key and Sounder

The sounder, Fig. 1, is made from an old electric-bell magnet, D, fastened to a wooden base.
The lever, A, can be made of brass and the armature, C, is made of iron.
The pivot, E, is made from a wire nail and is soldered to A. It should be filed to a point at each end so as to move freely in the bearings, B, which are pieces of hard wood.
The spring, H, is fastened at each end by pins, bent as shown, and should not be too strong or the magnet will be unable to move the armature.

SOUNDER
A. brass:
B. wood:
C. soft iron;
DD. coils wound with No. 26 wire:
E. nail soldered on A;
FF. binding posts:
H spring

The stop, K, is a wire nail driven deep enough in the base to leave about 1/8 in. between the armature and the magnet. The binding posts, F, may be taken from old dry batteries and are connected to the two wires from the magnet by wires run in grooves cut in the base.

The base of the key, Fig. 2, is also made of wood and has two wooden bearings, E, which are made to receive a pivot, similar to the one used in the sounder. The lever of the key is made of brass and has a hardwood knob, A, fastened near the end. A switch, D, connects with the pivot at F and can be either made from sheet brass, or taken from a small one-point switch. The binding posts are like those of the sounder, and are connected to the contacts, K, by wires run in grooves cut in the wood.

KEY
A. wood;
B. brass or iron soldered to nail;
C. brass;
D. brass:
E. wood:
F. connection of D to nail;
HH. binding posts

Excerpt from the book:
THE BOY MECHANIC
VOLUME I
700 THINGS FOR BOYS TO DO
WITH 800 ILLUSTRATIONS
1913, BY H. H. WINDSOR CHICAGO
POPULAR MECHANICS CO. PUBLISHERS